The dangers of being born too small or too soon

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Comment380 Vol 382 August 3, 2013*John E Morley, Alan SinclairDivision of Geriatric Medicine and Endocrinology, Saint Louis University School of Medicine, St Louis, MO 63104, USA (JEM); Bedfordshire and Hertfordshire Postgraduate Medical School, University of Bedfordshire, Luton, Bedfordshire, UK, and Institute of Diabetes for Older People, Luton, Bedfordshire, UK (AS) JEM has received consultancy fees from Sano , Nutricia, and Nestl. AS has received consultancy and lecture fees from Takeda, P zer, MSD, Merck, Sano , Novartis, and Lilly.1 Sinclair A, Morley JE, Rodriguez-Maas L, et al. Diabetes mellitus in older people: position statement on behalf of the International Association of Gerontology and Geriatrics (IAGG), the European Diabetes Working Party for Older People (EDWPOP), and the International Task Force of Experts in Diabetes. J Am Med Dir Assoc 2012; 13: 497502.2 Kirkman MS, Briscoe VJ, Clark N, et al, for the Consensus Development Conference on Diabetes and Old Adults. Diabetes in older adults: a consensus report. J Am Geriatr Soc 2012; 60: 234256.3 Migdal A, Yarandi SS, Smiley D, Umpierrez GE. Update on diabetes in the elderly and in nursing home residents. J Am Med Dir Assoc 2011; 12: 62732.e2.Birth is dangerous, especially for infants born too small or too soon. Although much is known about the mortality risk for such infants in high-income countries, little is known about the risk in poorer countries. In The Lancet, Joanne Katz and colleagues begin to ll in the gap on just how dangerous it is to be born too small or too soon in a low-income or middle-income country.1 The investigators analysed more than 2 million birth outcomes from resource-poor countries in Asia, Africa, and Latin America and calculated the regional risk of neonatal and post-neonatal mortality associated with being born preterm, small-for-gestational age (SGA), or both.Using data from 20 cohorts in 13 countries, Katz and colleagues show that being born SGA increased the risk of neonatal mortality by two to ve times across the three regions, but being born preterm ( Vol 382 August 3, 2013 381failure was detectable as early as 15 weeks of gestation, and infants tend to be born short and round.3 Infants of HIV-infected mothers on antiretroviral therapy in Haiti and Zambia were also born small, largely because of shortness at birth rather than thinness.4,5 There has been much discussion about the causes and consequences of proportional (ie, short and round) versus disproportional (long and thin) phenotypes of SGA babies, with some evidence that thin SGA babies are at higher risk of adverse outcomes.6,7 Elucidation of the di erences in mortality risk among types of SGA infants will require datasets that include infant length at birth, but such data are rare.Katz and colleagues ndings present important methodological challenges. The investigators included cohorts on the basis of completeness and quality of their data. Nonetheless, in six of the cohorts, they imputed some birthweights because some data were missing or measured too late. Some of the variability in birthweight might have resulted from the 72 h observation window used (during which breastfed neonates can lose up to 10% of their weight8). Unfortunately, the preferred reference dataset for calculating birthweight-for-gestational age (the Alex-ander reference9) provides data at only the tenth percentile, so the authors used a di erent reference dataset to identify infants below the third percentile.10 Both references are from large US populations, with data obtained in 197276 and 1991, respectively. The appropriateness of these reference populations, especially for the cohorts from South Asia, is unknown and might be among the factors that account for the high proportions of SGA births seen. Again, not knowing the excess mortality associated with the SGA babies who were term and not LBW, we wonder whether the use of the tenth percentile of the Alexander reference put too many babies in this risk category.The analysis presented by Katz and colleagues is a substantial contribution, and points the way to further advances. Most of the cohort studies included were not representative of the country where they were done, and the studies included in a given region were also not representative of that regioneg, the vast majority of data from Latin America was from Chile. More representative data are surely needed. Also, many low-income or middle-income countries are in eastern Europe and central Asia, regions not represented in these analyses. The scarcity of data from these regions, however, is because of a dearth of global resources and attention rather than a product of poor study design. We hope that this important study can serve as a catalyst for the development of stronger datasets that require fewer assumptions and include additional essential information, including length at birth.*Rebecca J Stoltzfus, Kathleen M RasmussenDivision of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USArjs62@cornell.eduWe declare that we have no con icts of interest.1 Katz J, Anne CCL, Kozuki N, et al. Mortality risk in preterm and small-for-gestational-age infants in low-income and middle-income countries: a pooled country analysis. Lancet 2013; 381: 41725. 2 Neufeld LM, Haas JD, Grajeda R, Martorell R. Ultrasound measurement of fetal size in rural Guatemala. Int J Gynaecol Obstet 2004; 84: 22028. 3 Ruel MT. The natural history of growth failure: importance of intrauterine and postnatal periods. In: Martorell R, Haschke F, eds. Nutrition and growth. Philadelphia: Nestec Ltd, Vevey/Lipincott Williams and Wilkins, 2001: 12357. 4 Arpadi S, Fawzy A, Aldrovandi GM, et al. Growth faltering due to breastfeeding cessation in uninfected children born to HIV-infected mothers in Zambia. Am J Clin Nutr 2009; 90: 34453. 5 Heidkamp RA. Evaluation of an infant feeding support strategy among HIV-exposed infants in urban Haiti. Ithaca: Cornell University, 2011. 6 Caul eld LE, Haas JD, Belizan JM, Rasmussen KM, Edmonston B. Di erences in early postnatal morbidity risk by pattern of fetal growth in Argentina. Paediatr Perinat Epidemiol 1991; 5: 26375. 7 Vik T, Markestad T, Ahlsten G, et al. Body proportions and early neonatal morbidity in small-for-gestational-age infants of successive births. Acta Obstet Gynecol Scand Suppl 1997; 165: 7681. 8 Chantry CJ, Nommsen-Rivers LA, Peerson JM, Cohen RJ, Dewey KG. Excess weight loss in rst-born breastfed newborns relates to maternal intrapartum uid balance. Pediatrics 2011; 127: e17179. 9 Alexander GR, Himes JH, Kaufman RB, Mor J, Kogan M. A United States national reference for fetal growth. Obstet Gynecol 1996; 87: 16368. 10 Oken E, Kleinman KP, Rich-Edwards J, Gillman MW. A nearly continuous measure of birth weight for gestational age using a United States national reference. BMC Pediatr 2003; 3: 6.The dangers of being born too small or too soonReferences